The objective of this research is to define rational indications for tonsillectomy and adenoidectomy, respectively, on the basis of the outcome of a prospective, controlled, clinical study. A subsidiary objective is to explore possible effects of removing tonsils or adenoids on certain presumed measures of immunologic competence. All patients referred from the out-patient clinics of the Children's Hospital of Pittsburgh for consideration of tonsil or adenoid surgery are seen in a special T&A Evaluation Clinic, where they receive detailed, standardized evaluation. From among this group potential candidates for adenoidectomy, or tonsillectomy, or both, are identified on the basis of stringent criteria for each procedure. These selected children are then randomly divided into surgical and control groups. Their clinical courses for extended periods thereafter will be compared with each other, and with those of patients not considered appropriate candidates for surgery. Differences, if any, among the three groups, in various parameters of health and disability, will be measured.